This invention relates to receptacle apparatus, and in particular to receptacle apparatus for housing components of lighting systems of the class utilized to equip commercial vehicles such as trucks, trailers, buses and the like. Such equipment must comply with legal regulations covering inter-state and intra-state traffic and includes lighting means of both the marker and clearance types to be mounted at sides and ends of a vehicle. In each type it is customary to employ enclosure bodies having readily detachable closure means to constitute lamp assemblies, junction boxes for receiving electrical wiring and terminals, as well as holder means in which certificates and other printed matter may be visibly contained and in some cases illuminated.
In the normal operating life of a commercial vehicle its lighting system is continuously exposed to road conditions which may necessitate frequent servicing of the components contained in receptacle apparatus. This may include replacement of lamp bulbs, cleaning of lens elements and checking electrical connections and switches. To provide for ready accessibility to components of this nature, the receptacle apparatus must include closure means which is readily detachable. A common practice is provision of an enclosure body around which a closure member is detachably secured by means of an O-ring.
Receptacle apparatus of this general class is well-known in the art as disclosed for example in U.S. Pat. No. 2,707,747. In this patent an O-ring is shown compressibly held between a housing and a lens member with matching grooves which are of circular cross-section. With this sealing arrangement, referred to as a static seal, the extent to which the O-ring may be compressed is limited by the grooves of circular cross-section and the sealing effect realized is understood to be not as effective as may be desired under some operating conditions, particularly where relatively large temperature fluctuations are experienced. Careful observance of required dimensional tolerances must be carried out in the manufacture of parts with matching grooves of circular cross-section in order that an adequate sealing effect may be maintained and combined with ready detachability.
In U.S. Pat. No. 3,244,869 greater compression of the O-ring is achieved by using ring-retaining grooves of rectangular cross-section designed to provide additional space into which O-ring portions may be forced. Here also very close tolerances must be observed in manufacture in order for the parts to provide an adequate seal and yet permit rapid "pry-off".
Moreover, both of the sealing arrangements disclosed in the above-noted patents are subject to drop in effectiveness of seal when exposed to temperature fluctuations and especially sharply lowered temperatures, and a need exists for improved sealing and methods of making improved sealing means.